CVE-2026-103603

Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7	Patch
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*

History

28 Oct 2026, 13:29

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
First Time		Bouncycastle bc-csharp Bouncycastle
CPE		cpe:2.3:a:bouncycastle:bc-csharp::::::::
References	~~() https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7 -~~	() https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7 - Patch
References	~~() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603 -~~	() https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603 - Patch, Vendor Advisory

02 Oct 2026, 08:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-02 08:17

Updated : 2026-10-28 13:29

NVD link : CVE-2026-103603

Mitre link : CVE-2026-103603

CVE.ORG link : CVE-2026-103603

JSON object : View

Products Affected

bouncycastle

bc-csharp

CWE

CWE-789

Memory Allocation with Excessive Size Value

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